Oh Door:
Many times I have seen the door ajar, mostly at night, and when I have tried to closed it some folks standing outside, usually smoking, had ask me to leave it like that.
On the other hand, when events are taking place I have noticed that the door its intentionally kept open to guide the newcomers that it is the entrance and they don't have to bother by ringing the bell, etc.
I don't have the solution to the whole door issue, but at least, I suggest, we should have a note in the inside stating to keep it closed at all times, of course, with exceptions when events are taking place.
--
Daniel